论文总字数：19861字

摘 要

膜分离技术已经被应用在废水处理和其再利用过程中，然而只有少数人关注陶瓷膜在速溶茶叶废水中的应用。本文研究中提出了一个综合的超滤（UF）过程来处理茶叶深加工废水。在这之前，废水将通过混凝组合技术进行预处理。聚合氯化铝铁（PAFC）作为絮凝剂被用于其中。通过实验确定最佳混凝条件是PAFC浓度800mg/L，pH值为5和温度20℃，同时阴离子聚丙烯酰胺（PAM）作为助凝剂的最佳投加量为20mg/L。然后将废水通过陶瓷膜超滤（UF）处理。在超滤过程中，我们研究了膜的孔径，跨膜压力（TMP）和错流速度（CFV）对膜通量以及浊度去除的效果。研究发现减少膜污染最佳的TMP和CFV为0.1MPa和3.0m/s。研究表明经过絮凝后的UF（0.05μm）膜通量高出未经预处理的膜通量的近3倍。根据Darcy定律，陶瓷膜的阻力及其分布被确定。对于0.02μm的陶瓷膜，其主要阻力是膜阻力。相较之下，0.05，0.2，0.5μm的陶瓷膜的主要阻力是不可逆阻力。使用FTIR、SEM、EDS表征膜表面的污染物，发现膜上的污染物主要是茶叶成分如茶多酚、糖类。研究表明絮凝是优良的预处理方式，可以有效提高陶瓷膜渗透通量。

关键词：膜分离技术 速溶茶废水 超滤 聚合氯化铝铁 最佳混凝条件

Cagulation–flocculation Process for the treatment of wastewater

from the production of instant tea powder

ABSTRACT

Integrated membrane processes have become an established technology in the treatment and reuse of wastewater. However, only a few people pay attention to the application of ceramic membranes in the instant tea powder wastewater. In this study, we proposed an integrated ultrafiltration (UF) process to treat the wastewater from an instant tea powder factory. Before this process, the wastewater was pretreated by combination of coagulation–flocculation. And polyaluminum ferric chloride (PAFC) was used as the coagulating agent. The optimum operating conditions with respect to contaminants removal were determined to be pH 5, 20^◦C and 800 mg/L of PAFC, with polyacrylamide (PAM) as coagulant aid at a dosage of 20 mg/L. Then the wastewater was treated with ceramic UF membranes. In the UF process, effects of membrane pore size, transmembrane pressure (TMP) and cross flow velocity (CFV) on permeate flux and rejections of turbidity was investigated. Optimal values of 0.1MPa and 3.0m/s were selected to reduce the membrane fouling. And it was confirmed that the permeate flux of UF membrane (0.05μm) was almost 3.0 times higher than typical flux obtained without pretreatment.According to Darcy’s Law, the membrane fouling resistances and their distribution were determined. The resistances against the permeate flux of 0.02μm ceramic membrane are considered to be mainly composed of the membrane resistance. Comparatively, the 0.05, 0.2 and 0.5 μm membranes, showed that the hydraulically irreversible resistance is the dominant factor.And FE-SEM micrographs, EDX and FTIR analysis indicated that the foulants were composed of the tea components, such as tea polyphenols and saccharide. The results highlighted by this work have shown that coagulation was an excellent pre-treatment which can obviously increase the permeate flux.

Key words: Integrated Membrane Process; Instant tea wastewater;coagulation–flocculation

目 录

摘要 I

ABSTRACT II

第一章 文献综述 1

1.1 选题背景 1

1.2无机絮凝剂 1

1.2.1无机低分子絮凝剂 1

1.2.2无机高分子絮凝剂 1

1.3有机絮凝剂 3

1.3.1合成有机高分子絮凝剂 3

1.3.2天然改性高分子絮凝剂 4

1.4微生物絮凝剂 5

1.5复合型絮凝剂 5

1.6展望 6

1.7研究意义 6

第二章 实验部分 8

2.1废水来源及水质 8

2.2实验仪器和药剂 8

2.2.1膜材料 8

2.2.2实验仪器 8

2.2.3实验试剂 9

2.3实验分析方法 9

2.3.1渗透通量测定方法 9

2.3.2截留率的表征 9

2.3.3膜阻力计算 10

第三章 实验分析结果 11

3.1 助凝剂的种类对混凝效果的影响 11

3.2混凝剂PAFC用量对混凝的影响 11

3.3 pH对混凝的影响 12

3.4温度对混凝的影响 13

3.5膜孔径对废水渗透通量的影响 14

3.6 TMP对膜渗透通量的影响 17

3.7 CFV对膜通量的影响 18

3.8 膜表面污染物的表征 19

第四章 结论与展望 21

4.1结论 21

4.2展望 21

参考文献 22

致谢 24

1. 文献综述

1.1 选题背景

水处理是通过物理、化学、生物的手段，去除水中一些对生产、生活不需要的有害物质的过程。是为了适用于特定的用途而对水进行的沉降、过滤、混凝、絮凝，以及缓蚀、阻垢等水质调理的过程。其中絮凝技术是目前国内外用来提高水质处理效率的一种既经济又简便的水处理技术，目前已广泛用于饮用水处理、废水处理、食品、化工、环保、发酵工业等诸多领域[1]。絮凝剂又称沉降剂, 是一类可使溶液中不易沉降的固体悬浮颗粒凝集、沉淀的物质。可定义为：凡是用来将水溶液中小的溶质、胶体或者悬浮物颗粒凝聚成絮状物沉淀的物质都叫做絮凝剂[2]。目前普遍应用的絮凝剂包括无机絮凝剂、有机絮凝剂、微生物絮凝剂及复合型絮凝剂等几大类。

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